The present invention relates in general to a molded article of manufacture and, more particularly, to a molded rotor blocking for use in a turbine generator within power generation plants.
Many power generation plants produce electricity by converting energy (e.g. fossil fuel, nuclear fusion, hydraulic head and geothermal heat) into mechanical energy (e.g. rotation of a turbine shaft), and then converting the mechanical energy into electrical energy (e.g. by the principles of electromagnetic induction). Some of these power generation plants, such as a fossil-fuel power generation plant, comprise a turbine, a generator and an exciter.
One aspect of the above-described power generation scheme involves use of rotor blockings to support, separate and insulate conductive windings in the generator rotor. The rotor blockings must withstand temperatures that can range from about xe2x88x9240xc2x0 C. to about 180xc2x0 C. and more typically from about xe2x88x9210xc2x0 C. to about 140xc2x0 C, and centrifugal loading at about 1500 RPM to about 4500 RPM and more typically at about 2000 RPM to about 3500 RPM. The rotor blockings come in a variety of sizes and shapes, and may also include channels that direct a flow of cooling fluid (e.g. air, hydrogen) over the conductive windings during generator operation. The rotor blocking should also be resistant to oil which is used for rotor shaft lubrication, as well as other detrimental substances found within the rotor.
As shown in FIGS. 1, heretofore, rotor blockings, and other articles of manufacture, typically have been constructed from a glass 10 and resin 12 composite material that is formed into laminate sheets 14 such as NEMA G-9 melamine-glass fabric, NEMA G10 and G11 epoxy-glass fabric, and NEMA GPO glass-polyester. These resin treated glass sheets 14 are stacked upon each other and orientated relative to each other to maximize the overall physical properties of the overall anisotropic composite material. The sheets 14 are then pressed during curing to achieve high temperature properties suitable for operation up to about 180xc2x0 C. The cured composite material is in the form of planar plates.
The cured composite material is then processed by CNC. machining or other similar means to form the composite material into the desired rotor blocking size and shape. The unused portions of the composite material are usually thrown away because recycling anisotropic composite scrap material is difficult and expensive.
There are many shortcomings, however, to the above-described rotor blocking and manufacturing process. One shortcoming involves the limited ways in which fibers within each layer of resin-glass fabric can be oriented with respect to the other resin-glass fabric layers and fibers. Another shortcoming involves the difficulty of incorporating materials other than sheets of resin or glass into the overall composite structure. Another shortcoming involves the relatively high cost of laminated plates of resin-glass fabric and the relatively high cost of CNC. machining a resin-glass material. For example, it costs several thousands of dollars of machine time and material costs to make a set of rotor blockings for a turbine generator, and laminate scrap from CNC. machining can constitute about 20-70% of the finished rotor block weight which adds up to thousands of dollars per turbine generator. Another shortcoming involves the significant number of rotor blocking defects caused by CNC. machining a resin-glass material, such as delamination, cracking and surface fracturing. Also, machining laminated materials degrades certain physical properties, such as strength and fatigue resistance. Another shortcoming involves the significant amount of space and number of operators needed to make rotor blockings by CNC machining a resin-glass material.
There is thus a need for an improved rotor blocking and an improved method of making a rotor blocking. There is also a more general need for an article of manufacture capable of withstanding temperatures that can range from about xe2x88x9240xc2x0 C. to about 180xc2x0 C. and preferably from about xe2x88x9210xc2x0 C. to about 140xc2x0 C., centrifugal loading at about 1500 RPM to about 4500 RPM and preferably at about 2000 RPM to about 3500 RPM while functioning as an insulator, and for a method of easily, flexibly, and inexpensively manufacturing that article.
The present invention provides a molded rotor blocking, or other article of manufacture, capable of withstanding temperatures that can range from about xe2x88x9240xc2x0 to about 180xc2x0 C. and preferably from about xe2x88x9210xc2x0 C. to about 140xc2x0 C., centrifugal loading at about 1500 RPM to about 4500 RPM and preferably at about 2000 RPM to about 4500 RPM, while functioning as an insulator. The rotor blocking is advantageously constructed of a thermoset resin matrix having glass fiber reinforcements embedded therein and manufactured from a molding process that can easily, flexibly and inexpensively form the rotor blocking into a desired size and shape.
The present invention also provides a relatively unlimited number of ways to arrange glass fibers or other reinforcements within a resin, and an easy way to incorporate materials other than sheets of thermoset prepreg into an overall composite structure.
The present invention also provides a composite material constructed from relatively low cost materials and made from a relatively low cost manufacturing process. For example, molding and material costs to make a set of rotor blockings for a turbine generator are just a few thousand dollars, and a negligible amount of raw material scrap is created.
The present invention also reduces, if not prevents, defects and degradation inherent from machining laminated composite materials, such as delamination, cracking, and fatigue resistance. Moreover, the present invention has a tougher skin layer that resists fracture initiation and provides stronger strength values versus machined parts under flexural, shear or torsional loading.
One aspect of the present invention thus involves a molded article of manufacture, comprising, a resin material selected from the group consisting of epoxy thermosets, polyester thermosets, cyanate ester, bismaleimide, phenolic, and melamine; and a reinforcement material selected from the group consisting of glass and mineral filler; wherein the molded article of manufacture is adapted to withstand temperatures that range from about xe2x88x9240xc2x0 C. to about 180xc2x0 C. and preferably from about xe2x88x9210xc2x0 C. to about 140xc2x0 C., and to withstand centrifugal loading at about 1500 RPM to about 4500 RPM at preferably at about 2000 RPM to about 3500 RPM while functioning as an insulator.
Another aspect of the present invention thus involves a molded rotor block adapted for use in a generator within a power generation unit, comprising, at least one thermoset resin material with a glass transition temperature above a maximum operating temperature of a conductive winding located within the generator; and at least one reinforcement material adapted to provide the molded rotor block with a suitable stiffness and strength to inhibit damage to the molded rotor block damage during normal operation of the generator.
Another aspect of the present invention thus involves a method of making of molded article of manufacture adapted to withstand temperatures that range from about negative 40xc2x0 C. to about 180xc2x0 C. and preferably from about negative 10xc2x0 C. to about 140xc2x0 C., and to withstand centrifugal loading at about 1500 RPM to about 4500 RPM and preferably at about 2000 RPM to about 3500 RPM while functioning as an insulator, comprising, placing a reinforcement material within a mold cavity; placing a resin material to the mold cavity; heating the mold cavity to a temperature of at least about 100xc2x0 C. for at least about 40 minutes to form the molded article of manufacture; and removing the formed molded article of manufacture from the mold cavity.
Further aspects, features and advantages of the present invention will become apparent from the drawings and detailed description of the preferred embodiment that follows.